Astronomers Discover 'Earth-Like' Planet

The most Earth-like planet yet has been discovered outside our solar system -- and its surface temperature averages a pleasant 72 degrees.

Researchers announced Monday at NASA's Ames Research Center in Moffett Field, Calif., that the planet was discovered by the Kepler space telescope and orbits a star about 600 light years away – within its "habitable" zone (and considered close by astronomical standards). "It is right smack in the middle of the habitable zone," Kepler scientist Natalie Batalha told USA Today.

The planet, named Kepler 22b, a rendering of which is shown above, could harbor oceans on its surface, like Earth does, since liquid water is considered vital for the development of life. The Kepler telescope also has discovered more than 1,000 new planet candidates, all of which require follow-up observations to verify they are actual planets.

Kepler-22b is about 2.4 times the radius of Earth, and scientists don't yet know if it has a predominantly rocky, gaseous or liquid composition.

Previous research hinted at the existence of near-Earth-size planets in habitable zones, but clear confirmation proved elusive. Two other small planets orbiting stars smaller and cooler than our sun recently were confirmed on the very edges of the habitable zone, with orbits more closely resembling those of Venus and Mars.

"This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington, in a press release. "Kepler's results continue to demonstrate the importance of NASA's science missions, which aim to answer some of the biggest questions about our place in the universe."